Monolithic Domes
One of the more imaginative systems for using shotcrete is Monolithic Domes' approach. They have pioneered the use of an inflated balloon-like structure which acts as a form for the eventual building. They actually have two different ways of doing this: one retains the fabric of the form as a part of the exterior of the building, and the other allows the form to be reused several times for other buildings. In the first instance, polyurethane foam insulation is spayed on the inside of the form and then allowed to set up. Then rebar is assembled beneath this to conform with the shape established, and the shotcrete to sprayed onto the steel reinforcing from the inside. Once this has set up, the resulting building is about as tough as anything made by man. Domes of this sort have withstood hurricanes and earthquakes; even cannonshot would not knock one of these down!